Comformable balloon devices and methods

ABSTRACT

The present disclosure is directed toward a semi-compliant to non-compliant, conformable balloon useful in medical applications. Conformable balloons of the present disclosure exhibit a low straightening force when in a curved configuration and at inflation pressures greater than 4 atm. Balloons of the present disclosure are constructed of material that can compress along an inner length when the balloon is in a curved configuration. In further embodiments, balloons of the present disclosure can be constructed of material that sufficiently elongates along an outer arc when the balloon is in a curved configuration. As a result, medical balloons, in accordance with the present disclosure, when inflated in a curved configuration, exhibit kink-free configurations and do not cause a significant degree of vessel straightening.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 15/231,494 filed on Aug. 8, 2016 and entitled “CONFORMABLE BALLOONDEVICES AND METHODS”, which is a continuation application of U.S.application Ser. No. 14/209,711 filed on Mar. 13, 2014 and entitled“CONFORMABLE BALLOON DEVICES AND METHODS”, now issued as U.S. Pat. No.9,669,194 on Jun. 6, 2017, which claims priority to U.S. ProvisionalApplication No. 61/786,022, filed on Mar. 14, 2013 and entitled“CONFORMABLE BALLOON DEVICES AND METHODS”, wherein the above-listedapplications are hereby incorporated by reference in their entireties.

FIELD

The present disclosure generally relates to medical balloons, and moreparticularly semi-compliant to non-compliant medical balloons that areconformable to a curved vessel.

BACKGROUND

There are two main types of mechanical stresses present during a typicalinflation of an elongated balloon. Hydraulic loading on a generallycylindrical balloon wall results in hoop stress and longitudinal stress.The result of the inflation loading depends on the type of material fromwhich the balloon walls are constructed. In simplified terms, for acompliant balloon, the load will result in the balloon adapting to theshape of surrounding constraints. For example, in a body vessel, theballoon will inflate up to contact with the vessel wall(s) and thencontinue to lengthen down the length of the vessel as more inflationmedium is introduced into the balloon. For non-compliant balloons, theshape is defined by the configuration of the balloon walls asmanufactured rather than surrounding constraints, and as inflationmedium is introduced, the pressure increases while the volume remainsrelatively constant. When a generally cylindrical non-compliant balloonis inflated in a curved vessel, the tendency is to maintain the moldedballoon shape, usually a straight shape, and thus stress the vesselwalls.

Percutaneous transluminal angioplasty (PTA) balloons, which aresemi-compliant to non-compliant balloons, are designed to operate atpressures between 5 to 30 atmospheres (“atm”) and do not readily conformto a curved configuration, in particular tortuous anatomies, e.g.,curved body vessels. More precisely, medical angioplasty balloons wheninflated in a curved configuration tend toward a straight configurationas the balloon is inflated to angioplasty pressures. This tendency tostraighten is characterized herein in terms of a straightening force. Asone might expect, such balloons, when extended along the vesselcurvature, are impeded from straightening by the surrounding vessel. Asa result, the balloon can cause unwanted straightening of, and damageto, the vessel, and/or the angioplasty balloon can kink. These balloonsdo not typically conform to the surrounding constraints, particularlywhen the surrounding constraints involve certain amounts of curvature.

Medical balloons capable of operating at angioplasty pressures yethaving a low or insignificant straightening force when in a curvedconfiguration can be useful in many applications.

SUMMARY

In accordance with one aspect of the disclosure, a medical balloon cancomprise a balloon wall material defining a chamber wherein a portion ofthe balloon wall along an inner arc undergoes at least 5% compressivestrain when inflated in a curved configuration requiring 20% strain;wherein said medical balloon is semi-compliant to non-compliant.

In accordance with another aspect of the disclosure, a medical balloonhaving a length along a longitudinal axis can comprise a balloon wallmaterial having a porous microstructure, wherein the balloon wallmaterial comprises a circumferential stiffness and a longitudinalstiffness and wherein the circumferential stiffness is at least 5 timesgreater than the longitudinal stiffness. In various embodiments, thecircumferential stiffness can be at least 8 times greater, 10 timesgreater, 15 times greater, 25 times greater, or 50 times greater thanthe longitudinal stiffness.

In accordance with another aspect of the disclosure, a method of makinga medical balloon can comprise wrapping an anisotropic, porous filmabout a mandrel having a diameter slightly greater than a nominaldiameter at an angle greater than 75 degrees with respect to alongitudinal axis to form a tubular precursor, wherein the tubularprecursor has a longitudinal stiffness that is at least 5 times lessthan a circumferential stiffness; and securing the tubular precursorabout a compliant bladder to form a balloon cover. During manufacture,the medical balloon may be inflated to the nominal diameter and thenradially compacted to a delivery profile, wherein, upon radialcompaction, the balloon cover forms a plurality of randomly orientedfolds that are much shorter than the length of the balloon, e.g., lessthan 20% of the balloon length.

In accordance with another aspect of the disclosure, a medical ballooncan comprise a balloon comprising a polymeric material and having anominal diameter between 3 mm to 8 mm and a nominal inflation pressureat or below 10 atm, where the balloon exhibits less than a 25% increasein mean straightening force when inflated from a pressure of 10 atm to16 atm while in a curved conformation requiring 16% total strain. Inaddition, other diameter balloons are also contemplated. For example, amedical balloon can comprise a balloon comprising a polymeric materialand having a nominal diameter between 9 mm to 12 mm and a nominalpressure at or below 6 atm, where the balloon exhibits less than a 3Nincrease in mean straightening force when inflated from a pressure of 5atm to 8 atm while in a curved conformation requiring 16% total strain.Also, a medical balloon can comprise a balloon comprising a polymericmaterial and having a nominal diameter between 13 mm to 14 mm and anominal inflation pressure at or below 6 atm, where the balloon exhibitsless than a 4N increase in mean straightening force when inflated from apressure of 6 atm to 8 atm while in a curved conformation requiring 16%total strain.

In accordance with another aspect of the disclosure, a medical ballooncan comprise a balloon comprising a polymeric material and having anominal diameter between 3 mm to 8 mm and a working pressure range thatspans a nominal inflation pressure to a rated burst pressure, where theballoon exhibits less than a 25% increase in mean straightening forcewhen inflated across the working pressure range while in a curvedconformation requiring 16% total strain, and where the nominal inflationpressure is at least 4 atm. In addition, other diameter balloons arealso contemplated. For example, a medical balloon can comprise a ballooncomprising a polymeric material and having a nominal diameter betweenabout 9 mm to about 12 mm and a working pressure range that spans anominal inflation pressure to a rated burst pressure, where the balloonexhibits less than a 3N increase in mean straightening force wheninflated across the working pressure range while in a curvedconformation requiring 16% total strain, and where the nominal inflationpressure is at least 4 atm. Also, a medical balloon can comprise aballoon comprising a polymeric material, and having a nominal diameterhaving the nominal diameter between about 13 mm to about 14 mm and aworking pressure range spans a nominal inflation pressure to a ratedburst pressure, where the balloon exhibits less than a 5N increase inmean straightening force when inflated across the working pressure rangewhile in a curved conformation requiring 16% total strain, and where thenominal inflation pressure is at least 4 atm.

In accordance with another aspect of the disclosure, a medical ballooncan comprise a balloon comprising a polymeric material and beinginflatable to a rated burst pressure, the balloon having a nominaldiameter of 3 mm to 12 mm where at the rated burst pressure, the balloonexhibits a straightening force as a function of balloon diameter (d) ofless than 0.86 (Diameter)+0.20 when in a curved conformation requiring16% total strain, where the rated burst pressure is at least 4 atm.

In accordance with another aspect of the disclosure, a medical ballooncan comprise a balloon comprising a polymeric material that can becomeplastically deformed upon inflation of the balloon to a pressure withinthe working pressure range such that when inflated in a curvedconfiguration having a bend radius and requiring 16% strain, the balloonupon re-inflation, without any surrounding constraints and to a pressurewithin the working pressure range, comprises a curved configurationhaving a bend radius that is less than 200% larger than the initial bendradius. Said balloon is semi-compliant to compliant.

The various aspects of the present disclosure can comprise a variety ofadditional or alternative features in any combination. In variousembodiments, the balloon wall material can remain kink-free wheninflated in said curved configuration. Said medical balloon can besemi-compliant to non-compliant. The balloon wall material can comprisea porous microstructure, such as one comprising a node and fibrilmicrostructure and/or be fibrillated. The porous microstructure can beexpanded polytetrafluoroethylene. In various embodiments, a portion ofthe balloon wall material along an inner arc undergoes at least 5%compressive strain when inflated in a curved configuration requiring 20%total strain. In various embodiments, the curved configuration can besuch that the portion of the balloon wall material along the inner arcundergoes compressive strain that is at least 30% of the total strain.Similarly, in various embodiments, the curved configuration can require25% total strain and the portion of the balloon wall material along theinner arc undergoes at least 10% compressive strain. In variousembodiments, the working length of the balloon lengthens less than 10%during inflation to at least an angioplasty pressure. In variousembodiments, the balloon wall material can remain kink-free when theratio of a balloon diameter within a working length to a bend radius isat least 1:3. In various embodiments, the medical balloon can furthercomprise a compliant bladder, such as an elastomeric bladder. Thenominal inflation pressures of the conformable balloon in a curvedconfiguration can be greater than 4 atm, greater than 8 atm, greaterthan 12 atm, greater than 16 atm, greater than 20 atm, or more andremain kink-free. In various embodiments, the balloon wall materialcomprises a circumferential stiffness greater than 200 gf/mm/mm. Invarious embodiments, the balloon wall material comprises acircumferential stiffness and a longitudinal stiffness and wherein thecircumferential stiffness is at least 5 times greater than thelongitudinal stiffness. For example, the longitudinal stiffness can beless than 30 gf/mm/mm for a medical balloon having a 4 mm diameter. Invarious embodiments, the microstructure of the balloon wall material canbe oriented at an angle greater than 80 degrees relative to thelongitudinal axis when inflated to the nominal diameter. In variousembodiments, the balloon wall material can comprise a membrane whereinthe membrane has a balance ratio of at least 10:1. In variousembodiments, the balloon wall material can be adapted to perfuse. Invarious embodiments, the balloon can form varied surface by way of atemplate having at least one aperture and overlying at least a portionof the balloon wherein the balloon wall material protrudes through theaperture in an inflated configuration. In various embodiments, the outersurface of the medical balloon can be coated with a therapeutic agentand/or utilized for the deployment or touching up of an endoprostheticdevice. For example, in various embodiments, the medical balloon cancomprise a stent or stent graft disposed about the balloon in a deliveryconfiguration.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present disclosure will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, wherein:

FIG. 1a illustrates a medical balloon embodiment in accordance with apresent disclosure, inflated in a curved configuration.

FIG. 1b illustrates a medical balloon embodiment in accordance with apresent disclosure, inflated in a straight configuration.

FIG. 1c illustrates a schematic view of the cross-section of a medicalballoon embodiment in accordance with a present disclosure.

FIG. 1d illustrates a medical balloon embodiment in accordance with apresent disclosure, inflated in a curved configuration and having atherapeutic agent coated thereon.

FIG. 1e illustrates a medical balloon embodiment in accordance with apresent disclosure, inflated in a curved configuration and having amedical device disposed about said medical balloon.

FIG. 2a illustrates a perfusable, a medical balloon embodiment inaccordance with a present disclosure.

FIG. 2b illustrates a schematic view of the cross-section of aperfusable, medical balloon embodiment in accordance with the presentdisclosure.

FIG. 3a illustrates a medical balloon embodiment in accordance with apresent disclosure adapted to form protrusions on the outer surface.

FIG. 3b illustrates a schematic view of the cross-section of a medicalballoon embodiment in accordance with a present disclosure adapted toform protrusions on the outer surface.

FIG. 4 illustrates a method of making a medical balloon embodiment inaccordance with a present disclosure.

FIG. 5 illustrates a method of using a medical balloon embodiment inaccordance with a present disclosure.

FIGS. 6a-6c depict images of a nylon balloon in a bent configuration asdescribed in Example 3.

FIGS. 7a-7c depict images of a medical balloon embodiment in accordancewith a present disclosure in a bent configuration as described inExample 3.

FIG. 8 is a table of data showing balance ratios of the balloon wallmaterials of both commercially-available PTA balloon devices and variousballoon embodiments in accordance with the present disclosure asdescribed in Example 5.

FIGS. 9a-9d are reproduction sketches of fluoroscopy images of variousballoon devices as set forth in Example 6 inflated in a curved vessel.The animal model and vessel location within the animal model (i.e.,where the balloon was inflated) were the same for FIGS. 9a and 9d andfor FIGS. 9b and 9c . As such, the relative amount of vessel deformation(or straightening) can be inferred from the shape of the balloon and thecatheter. The conformable balloons of FIGS. 9a and 9b exhibit a morecurved shape and minimal, if not any, vessel straightening. In addition,the shoulders on the conformable balloons of FIGS. 9a and 9b are notdeformed, and the guidewire is generally centered between the shouldersat both ends of the balloon. This is indicative of less stress at theends as compared to the balloons of FIGS. 9c and 9 d.

FIG. 10 is a schematic curve as described in Example 3.

FIGS. 11a-11d illustrate the setup of the Instron 3-point bend fixturefor a 3 mm, a 5 mm, an 8 mm, and a 12 mm balloon, respectively.

FIG. 12 is a table of data showing the straightening force measurementstaken of various balloons in a 3-point bend fixture as described inExample 11.

FIG. 13a is a plot showing the straightening force as a function ofpressure of a 3 mm nominal diameter balloon made in accordance with thepresent disclosure compared to a Abbott “FoxCross” 3 mm balloon asdescribed in Example 11.

FIG. 13b is a plot showing the straightening force as a function ofpressure of a 5 mm nominal diameter balloon made in accordance with thepresent disclosure compared to a Abbott “FoxCross” 5 mm balloon asdescribed in Example 11.

FIG. 13c is a plot showing the straightening force as a function ofpressure of a 8 mm nominal diameter balloon made in accordance with thepresent disclosure compared to other 8 mm PTA balloons, namely, the Bard“Conquest” balloon; the Abbott “FoxCross” balloon; and the AngioDynamics“Workhorse” balloon as described in Example 11.

FIG. 13d is a plot showing the straightening force as a function ofpressure of a 12 mm nominal diameter balloon made in accordance with thepresent disclosure compared to a Abbott “FoxCross” 12 mm balloon asdescribed in Example 11.

FIG. 14a is a graph plotting the straightening force at the rated burstpressure for a 3, 5, 8, and 12 mm conformable balloon and the thresholdtrend lines, and FIG. 14b shows the straightening force at the ratedburst pressure for the 3 mm conformable balloon and the lower end pointof the threshold trend lines.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Persons skilled in the art will readily appreciate that various aspectsof the present disclosure can be realized by any number of methods andapparatuses configured to perform the intended functions. Stateddifferently, other methods and apparatuses can be incorporated herein toperform the intended functions. It should also be noted that theaccompanying drawing figures referred to herein are not all drawn toscale, but may be exaggerated to illustrate various aspects of thepresent disclosure, and in that regard, the drawing figures should notbe construed as limiting. Finally, although the present disclosure maybe described in connection with various principles and beliefs, thepresent disclosure should not be bound by theory.

As used herein, “straightening force” means the amount of force exertedby the balloon on to a constraint as the balloon attempts to return to astraight state. One technique for measuring the amount of straighteningforce is set forth in Example 11, where the constraint is a 3-point bendfixture.

As used herein, “strain” means the deformation of a material caused byapplying an external force to it.

As used herein, “compressive strain” means an amount of materialdeformation caused by applying a compressive force to a material, i.e.,negative strain. Compressive strain can be understood as in-planecompression as distinguished from macro buckling or folding of amaterial.

As used herein, “tensile strain” means an amount of material deformationcaused by applying a tensile force to a material.

As used herein, “nominal diameter” means the approximate diameter of theballoon at the nominal inflation pressure. Beyond this state, pressureincreases (e.g., up to the rated burst pressure) result in less than a20% increase in diameter, less than a 15% increase in diameter, or lessthan a 10% increase in diameter.

As used herein, “angioplasty pressure” means the minimum pressurerequired to perform a PTA procedure for a balloon of a certain size.This value is dependent on the size of the balloon, and can be withinthe working pressure range between the nominal inflation pressure to therated burst pressure, the nominal inflation pressure being the minimumpressure at which the balloon reaches nominal diameter and rated burstpressure being the upper limit of a pressure range for a medical balloonprovided by the manufacturer.

As used herein, “balance ratio” means ratio of machine direction matrixtensile strength to transverse direction matrix tensile strength. Wherethe matrix tensile strengths in the machine and transverse direction arenot substantially equal, a material can be said to be “anisotropic.”

As used herein, “stiffness” is a measure of the change in load over anincrease or decrease in tested length. Stiffness differs from modulus asit is not normalized for cross sectional area or for gauge length.Modulus is change in stress over change in strain.

As used herein, a “semi-compliant to non-compliant” balloon is one thathas less than about 20% diametric growth (e.g., less than a 20% increasein the balloon diameter relative to the nominal diameter) when inflatedfrom the nominal inflation pressure to the rated burst pressure.Balloons of the present disclosure are semi-compliant to non-compliant,and after reaching the nominal inflation pressure, can exhibit less 20%diametric growth, less than 15% diametric growth, or less than 10%diametric growth.

As used herein, “medical device” means any medical device capable ofbeing implanted and/or deployed within a body lumen or cavity. Invarious embodiments, a medical device can comprise an endovascularmedical device such as a stent, a stent-graft, graft, heart valve, heartvalve frame or pre-stent, occluder, sensor, marker, closure device,filter, embolic protection device, anchor, drug delivery device, cardiacor neurostimulation lead, gastrointestinal sleeves, and the like.

As used herein, “kink” means a fold, pleat, wrinkle, or similar deformedcondition.

As used herein, “mean straightening force” means the mean force measuredover the time span that the balloon was held at a specific pressure.

Lastly, the preposition “between,” when used to define a range of values(e.g., between x and y) means that the range includes the end points(e.g., x and y) of the given range and the values between the endpoints.

The present disclosure is directed towards a semi-compliant tonon-compliant, conformable balloon useful for medical applications.Conformable balloons of the present disclosure exhibit a low orinsignificant straightening force when in a curved configuration and atinflation pressures greater than 4 atm. Balloons of the presentdisclosure are constructed of material(s) that can compress along aninner arc length when the balloon is in a curved configuration. Infurther embodiments, balloons of the present disclosure can beconstructed of material that sufficiently elongates along an outer arclength when the balloon is in a curved configuration. As a result,medical balloons, in accordance with the present disclosure, can conformto the surrounding curved anatomy. When inflated in a curvedconfiguration, these conformable medical balloons exhibit kink-freeinflation and do not cause a significant degree of straightening of bodyanatomies or “tortuous paths” (e.g., blood vessels), if any at all, atinflation pressures greater than 4 atm.

In addition, the balloon embodiments of the present disclosure canprovide substantially uniform vessel contact (“apposition”) along theirworking lengths or intermediate sections. By contrast, if a kink occurs,there will not be uniform vessel contact along the working length. Thedescribed embodiments can also provide generally uniform pressure alongtheir working lengths to the entire circumference of a curved anatomy.By contrast, if a kink occurs, there will not be uniform pressure alongthe working length. Uniform contact and uniform pressures on a curvedvessel, for example, can facilitate a more efficient delivery of atherapeutic agent for such embodiments coated with a therapeutic agent.Similarly, uniform contact and uniform pressures on a curved vessel, forexample, can facilitate improved device deployment for such embodimentshaving a deployable device mounted thereon.

The balloon embodiments of the present disclosure can comprise afluid-tight, compliant bladder so that the balloon does not perfuse.Alternatively, described embodiments can be bladderless and constructedto perfuse at a desired threshold pressure or diameter.

The balloon embodiments of the present disclosure can be part of aballoon assembly adapted to form a protruding topography on the balloonsurface. A template having at least one aperture can be located about anunderlying conformable balloon. The template is constructed not tocircumferentially or longitudinally distend to the same extent as theunderlying balloon, thus, at least one surface protrusion would form.Said constructs can be fluid tight or configured to perfuse as well.

According to the present disclosure, with reference to FIGS. 1a-1c , amedical balloon 100 comprises a balloon wall 110 defining a chamber 106wherein a portion of the balloon wall 110 along an inner arc 111undergoes at least 5% compressive strain when inflated in a curvedconfiguration that requires 20% total strain. As the balloon 100 can besemi-compliant to non-compliant, it is capable of inflation pressureswithin the range of at least about 4 atm to about 30 atm or more and hasless than about 20% diametric growth from the nominal inflation pressureto the rated burst pressure. For example, a working pressure range canbe between about 5 atm to about 9 atm, about 9 atm to about 20 atm, orany range within either of these ranges. The medical balloon 100 remainskink-free when inflated to an angioplasty pressure in the specifiedcurved configuration. The balloon 100 of the present disclosure wheninflated to at least the angioplasty pressure is capable of retaining akink-free at curved configuration requiring total strain amounts higherthan 20%.

The range of curvature wherein a kink-free inflation can be maintaineddepends on the dimension of the balloon. In various embodiments, themedical balloon can have a kink-free, curved configuration such that thebend radius is at least three times greater than the balloon diameter asmeasured within a working length of the balloon 100, e.g., the nominaldiameter. In various embodiments, the medical balloon 100 can have acurved configuration such that the ratio of bend radius to balloondiameter is about 2:1; about 3:1; about 4:1; about 5:1; about 6:1; about7:1; about 8:1; about 9:1; about 10:1; about 11:1; about 12:1; about13:1; or about 14:1 or more.

The balloon wall 110 comprises a material layer that is compressible,elongatable, or a combination of the two, along the length of theballoon 100. Stated differently, the balloon wall 110 can undergocompressive strain along the portion of the wall 110 defining the innerarc 111 and/or tensile strain along the portion of the balloon walldefining the outer arc 112 when inflated in a curved configuration. Invarious embodiments, the relative amount of compressive strain can bebetween about 25% to about 100% of the total strain. Accordingly, wheninflated in a curved configuration, the balloon wall 110 can adapt tothe changes in length along the portion of the working length of theballoon defining an inner arc 111 and outer arc 112.

In various embodiments, the balloon wall 110 is capable of undergoing atleast 5% compressive strain or at least 10% compressive strain, e.g.,along the section or sections of the balloon wall 110 that extend alongthe inner arc 111 of the balloon in a curved conformation. For example,the balloon wall 110 comprises a porous material that facilitatescompressive strain along a lengthwise section. Such section of balloonwall 110 can be at least a 5 mm lengthwise section extending along innerarc 111, such as the 1 cm lengthwise section measured in Example 3 todetermine compressive strain. While not wishing to be bound by aparticular theory, it is believed that compression is facilitated by thevoid spaces of the porous material that allow for the material bulk tocompress and thus reduce the volume of the void spaces.

In various embodiments, a porous material can comprise an expandedpolymeric film. In addition, the pores of at least a portion of theporous material can be devoid of any material that can impedecompression; e.g., the porous material comprises a plurality ofcompressible voids. For example, the porous material can comprise a nodeand fibril microstructure that is free of any imbibed material. Inaddition, the architecture of porous microstructure can be substantiallyfibrillated (e.g., a non-woven web having a microstructure ofsubstantially only fibrils, some fused at crossover points or withsmaller nodal dimensions). Large nodes or large densified regions mayhave an impact on the extent of compressibility or compressivestiffness.

In various embodiments, the porous material comprises expandedpolytetrafluoroethylene (ePTFE), expanded polyethylene, woven andnon-woven fabrics or films, and the like. Non-limiting examples ofexpandable fluoropolymers include, but are not limited to, expandedPTFE, expanded modified PTFE, and expanded copolymers of PTFE. Patentshave been filed on expandable blends of PTFE, expandable modified PTFE,and expanded copolymers of PTFE, such as, for example, U.S. Pat. No.5,708,044 to Branca; U.S. Pat. No. 6,541,589 to Baillie; U.S. Pat. No.7,531,611 to Sabol et al.; U.S. patent application Ser. No. 11/906,877to Ford; and U.S. patent application Ser. No. 12/410,050 to Xu et al.

While in some embodiments the porous material is free of any imbibedmaterials, in various other embodiments, the porous material cancomprise light imbibing and/or sectional imbibing that facilitatesballoon compaction or retraction upon deflation but does notsignificantly impact the ability to undergo compressive strain and/ortensile strain. Such imbibed materials can comprise an elastomer, suchas a polyurethane (such as an aromatic polyurethane like Techothane), athermoplastic fluoroelastomer copolymer oftetrafluoroethylene/perfluoromethylvinylether (TFE/PMVE) as taught inU.S. Pat. No. 7,049,380 and U.S. Pat. No. 8,048,440, both to Chang etal., silicone, FKM designated fluoroelastomers according to ASTM D1418(e.g, Viton by DuPont), and/or silicone rubbers. The weight ratio ofporous material to imbibed elastomer in the balloon wall 110 can be atleast 1:3, 1:2, 2:3, 1:1, 3:2, 2:1, 3:1, 4:1, 5:1 6:1, 7:1, 8:1, 9:1,10:1, 15:1, 18:1, 19:1, 20:1, or any ratio or range therebetween. Insome embodiments, the weight ratio of porous material to imbibedelastomer can be between 2:3 and 3:2. In various embodiments, theballoon wall 110 can be formed from wrapped layers wherein a certainpercentage of layers comprise an imbibed porous material. For example,the balloon wall 110 can comprise wrapped layers of porous material,wherein up to 50%, up to 30%, up to 20%, up to 15%, up to 10%, up to 5%,or up to 2% of the wrapped layers are imbibed with an elastomer. In someembodiments, 5% to 30% of the wrapped layers are imbibed with anelastomer. Alternatively or in addition thereto, in various embodiments,a discrete circumferential section of the porous material of balloonwall 110 can be imbibed with an elastomer.

In different or the same embodiments, the material layer can beanisotropic, oriented such that the balloon wall is weaker in thelongitudinal direction than the radial direction. The longitudinalstiffness is sufficiently low to provide for some elongation (tensilestrain) on the outer arc 112. The preferred amount of longitudinalstiffness can vary with the dimensions (width and length) of theballoon. For example, an 8 mm diameter balloon can have a longitudinalstiffness less than 70 gf/mm/mm, or a 4 mm diameter balloon can have alongitudinal stiffness less than 30 gf/mm/mm. In general, thelongitudinal stiffness (also referred to herein as “tensile stiffness”)of the anisotropic layer will be sufficiently low so that the balloondoes not significantly reorient toward a straight configuration wheninflated in a curved configuration at angioplasty pressures greater than4 atm or more.

While a low longitudinal stiffness facilitates tensile strain along theouter arc 112, in various embodiments, there can be a lower limit to theamount of longitudinal stiffness. Again, the lower limit can depend onthe dimensions of the balloon 100. Tensile strain along the outer arc112 can result in the working length 101 of the balloon 100 lengtheningto some degree. While reduced longitudinal stiffness in the balloon wall110 can contribute to a lower straightening force, being too low canresult in excessive lengthening. Excessive lengthening can in manyapplications be undesirable, and the extent of lengthening should becontrolled for a desired pressure. By appropriately selecting thelongitudinal stiffness, the working length 101 of the balloon 100, inaccordance with the present disclosure, can lengthen less than 10%during inflation to an angioplasty pressure.

In addition, in various embodiments, the balloon wall 110 can morereadily compress along the inner arc 111 than distend along the outerarc 112. In other words, the material layer can comprise a compressivestiffness less than the tensile stiffness.

The total strain can be calculated by the method described in Example 4.By way of example, an 8 mm balloon in a 32 mm bend radius requires about11 to 25% total strain to have a low or insignificant straighteningforce and/or remain kink-free. The precise value is dependant on themanner in which material layer responds to being stressed when in acurved conformation. A material layer can exhibit equal amounts ofcompressive and tensile strain amounting to 22.2% total strain (11.1% onthe inner radius and 11.1% on the outer radius); all compressive strainresulting in 20% total strain; all tensile strain resulting in 25% totalstrain; or any strain amount there between.

In accordance with the present disclosure, the circumferential stiffnessof the balloon wall 110 is sufficiently high to facilitate control ofthe maximum diameter at the rated burst pressure. In accordance withvarious embodiments, the balloon wall 110 can comprise a circumferentialstiffness of at least 200 gf/mm/mm for 8 mm balloons and 100 gf/mm/mmfor 4 mm balloons. In various embodiments, the balloon wall 110comprises a circumferential stiffness and a longitudinal stiffness andwherein the circumferential stiffness is at least 5 times greater thanthe longitudinal stiffness. In various embodiments, the balance ratio ofthe material layer can be 3:1 up to 100:1, e.g., at least 10:1. Asufficiently high circumferential stiffness may also facilitate at leastpartially a preferential failure mode at the ends of the balloon 100,typically at its seals 104 and/or 105.

To construct the material layer in the desired orientation, the materialof the balloon wall 110 can comprise an oriented anisotropic film.Orientation refers to the general direction of the microstructurefeatures, e.g., the fibrils. In various embodiments, the wall 110comprises a material that is helically oriented at a high angle. Forexample, the material of wall 110 can have a fibril orientation of atleast 75 degrees relative to the longitudinal axis of balloon 100; andin further embodiments, the material of wall 110 can have a fibrilorientation of between 80 degrees to 86 degrees. In this instance, theanisotropic film being wrapped at a high angle comprises a high strengthin the direction that is oriented at the high wrap angle (in otherwords, the higher strength of the balloon wall 110 is generally orientedaround the circumference and the weaker direction is generally orientedalong the length of the balloon).

In accordance with the present disclosure, the material of balloon wall110 can become plastically deformed upon inflation to a pressure withinthe working pressure range such that when inflated in a curvedconfiguration defined by a bend radius and requiring 16% strain, theballoon 100 upon re-inflation, without any surrounding constraints andagain to a pressure within the working pressure range, will have acurved configuration that comprises a bend radius that is less than 200%larger than the initial bend radius or less than 150% larger than theinitial bend radius. In addition, upon re-inflation, the diameter of theballoon will remain within the semi-compliant to non-compliant range.

The described medical balloon can have any appropriate dimension for theclinical application and can be generally cylindrical along the workinglength 101. The working length 101 of the balloon 100 can be about 10 mmto about 150 mm or more. Similarly, the diameter of the balloon 100 canbe about 2 mm to about 30 mm or more. By way of example, a balloon 100can have a 4 mm diameter and a 30 mm working length, or alternatively,an 8 mm diameter and about a 60 mm working length. Of course, theballoon 100 of the present disclosure can be constructed at anydimensions appropriate for the specific use.

The described medical balloon 100 mounted on an elongate member 150,such as a catheter or a hypotube, can have good trackability through thevasculature. In various embodiments, the described medical balloon 100can be concentrically crushed to a profile for delivery as opposed tobeing longitudinally pleated and folded thus having random, numerous,and relatively smaller folds and creases. While not wishing to be boundby any particular theory, it is believed that the longitudinal pleatsresult in added longitudinal rigidity to the corresponding section ofthe elongate member 150, whereas random folds in a variety of directionscontribute less to the longitudinal rigidity.

The described medical balloon 100 can be used for a number ofapplications traditionally performed by other semi-compliant tonon-compliant balloons. Medical balloon 100 can be used to perform a PTAprocedure, deploy or seat a medical device, deliver a drug, deliver RFenergy, and/or in any other procedure that would benefit from itsproperties. When used to deploy, seat, touch-up, or otherwise positionmedical devices, the described balloon can be used in conjunction withany such devices, such as balloon expandable or self-expanding stents orstent grafts, or other endoluminal devices.

By way of example, with reference to FIG. 1d , the balloon 100 inaccordance with the present disclosure can be coated with a therapeuticagent 160. In further embodiments, a retractable sheath (not shown) canbe located about the balloon 100 to prevent or minimize release of saidtherapeutic agent 160 until the balloon 100 is at the desired treatmentsite.

A “therapeutic agent,” as used herein, is an agent that can a bioactiveresponse or be detectable by an analytical device. Such agents include,but are not limited to, radiopaque compounds, cilostazol, everolimus,dicumarol, zotarolimus, carvedilol, anti-thrombotic agents such asheparin, heparin derivatives, urokinase, and dextrophenylalanine prolinearginine chloromethylketone; anti-inflammatory agents such asdexamethasone, prednisolone, corticosterone, budesonide, estrogen,sulfasalazine and mesalamine, sirolimus and everolimus (and relatedanalogs), anti-neoplastic/antiproliferative/anti-miotic agents such asmajor taxane domain-binding drugs, such as paclitaxel and analoguesthereof, epothilone, discodermolide, docetaxel, paclitaxel protein-boundparticles such as ABRAXANE® (ABRAXANE is a registered trademark ofABRAXIS BIOSCIENCE, LLC), paclitaxel complexed with an appropriatecyclodextrin (or cyclodextrin like molecule), rapamycin and analoguesthereof, rapamycin (or rapamycin analogs) complexed with an appropriatecyclodextrin (or cyclodextrin like molecule), 17β-estradiol,17β-estradiol complexed with an appropriate cyclodextrin, dicumarol,dicumarol complexed with an appropriate cyclodextrin, β-lapachone andanalogues thereof, 5-fluorouracil, cisplatin, vinblastine, vincristine,epothilones, endostatin, angiostatin, angiopeptin, monoclonal antibodiescapable of blocking smooth muscle cell proliferation, and thymidinekinase inhibitors; anesthetic agents such as lidocaine, bupivacaine andropivacaine; anti-coagulants such as D-Phe-Pro-Arg chloromethyl ketone,an RGD peptide-containing compound, AZX100 a cell peptide that mimicsHSP20 (Capstone Therapeutics Corp., USA), heparin, hirudin, antithrombincompounds, platelet receptor antagonists, anti-thrombin antibodies,anti-platelet receptor antibodies, aspirin, prostaglandin inhibitors,platelet inhibitors and tick antiplatelet peptides; vascular cell growthpromoters such as growth factors, transcriptional activators, andtranslational promotors; vascular cell growth inhibitors such as growthfactor inhibitors, growth factor receptor antagonists, transcriptionalrepressors, translational repressors, replication inhibitors, inhibitoryantibodies, antibodies directed against growth factors, bifunctionalmolecules consisting of a growth factor and a cytotoxin, bifunctionalmolecules consisting of an antibody and a cytotoxin; protein kinase andtyrosine kinase inhibitors (e.g., tyrphostins, genistein, quinoxalines);prostacyclin analogs; cholesterol-lowering agents; angiopoietins;antimicrobial agents such as triclosan, cephalosporins, aminoglycosidesand nitrofurantoin; cytotoxic agents, cytostatic agents and cellproliferation affectors; vasodilating agents; agents that interfere withendogenous vasoactive mechanisms; inhibitors of leukocyte recruitment,such as monoclonal antibodies; cytokines; hormones or a combinationthereof. In one embodiment, said therapeutic agent is a hydrophilicagent. In another embodiment, said therapeutic agent is a hydrophobicagent. In another embodiment, said therapeutic agent is paclitaxel.

By way of second example, with reference to FIG. 1e , balloon 100 inaccordance with the present disclosure can comprise medical device 170disposed about balloon 100. Balloon 100 can be used to expand or touchup medical device 170. As shown, medical device 170 is a stent, and moreparticularly a segmented stent, e.g., a stent comprising a plurality ofdiscrete annular stent members. As previously mentioned, the stent canbe balloon-expandable or self-expanding.

In various embodiments, again with reference to FIGS. 1a to 1c , themedical balloon 100 comprises a generally cylindrical form that issecured to the elongate member 150 at its proximal and distal ends. Theballoon 100 has a body portion 101 across the intermediate section,which is also be referred to as the working length. This section is thesection of the balloon 100 that reaches the nominal diameter in theinflated state. The balloon proximal shoulder 102 and distal shoulder103 are the sections of the balloon 100 lying between the proximal seal104 and distal seal 105 and the body portion 101. In variousembodiments, the shoulders 102, 103 are not conical in shape but aremore akin to a rounded corner of a square. In various other embodiments,the shoulders 102, 103 comprise a conical shape or conical steppedshoulders. For example, shoulder 102, 103 of material layer can comprisea non-distensible material that gives the shoulders a conical shape or astepped conical shape. Radiopaque markers or other detectable markermechanisms can be used to indicate the working length 101 of the balloon100. The markers can be located on the underlying elongate member 150 orwithin or on the balloon wall 110.

In various embodiments, the balloon 100 can further comprise a compliantbladder 120, such as an elastomeric bladder to facilitate a fluid tightdevice. In various embodiments, the compliant bladder 120 can bedetached from wall 110 along at least a portion of the length includingthe working length 101 and shoulders 102 and 103 or the entire length.In other embodiments, the compliant bladder 120 is attached to the wall110 along at least a portion of said length or the entire length. Thecompliant bladder 120 can be an inner layer about which the materiallayer is situated. The compliant bladder can possess properties that donot consequentially impact the balloon inflating kink-free in a curvedconfiguration.

In various embodiments, with reference to FIGS. 2a to 2b , the balloon100 does not have a compliant bladder and thus is capable of perfusion.For example, balloons 100 are disclosed that expand to a nominaldiameter and perfuse in response to an internal pressure exceeding athreshold pressure. In such a manner, in various embodiments, theballoon 100 can be inflated to a first pressure sufficient for theballoon 100 to reach the nominal diameter. Then, at a desired time, theinternal pressure can be increased from the first pressure, causingperfusion of the inflation fluid 240 through the balloon wall 110without a significant increase in balloon diameter. Stated another way,balloons, in accordance with various embodiments, have a water entrypressure (“WEP”) and/or bubble point tailored to be at or above thatwhich is required for inflation to a fixed diameter. For example, invarious embodiments, the balloon 100 can inflate to a nominal diameterat a pressure below the WEP and/or bubble point and then additionalinternal pressure can be exerted to reach or exceed the WEP and/orbubble point. Thus, expansion and perfusion can be independentlycontrollable. In various embodiments, the inflation fluid can comprise atherapeutic fluid 240.

In various embodiments, with reference to FIGS. 3a to 3b , the balloon100 can further comprise a template 330 having at least one aperture 331and overlying at least a portion of the balloon wall 110 wherein theballoon wall 110 protrudes through the aperture 331 in an inflatedconfiguration, producing protrusion 332. The template 330 can similarlybe anisotropic, except the template 330 comprises the same or a slightlyhigher amount of longitudinal stiffness and/or a circumferentialstiffness greater than that of the balloon wall 110. As such, thetemplate 330 will expand and/or elongate at a lower rate per increase ininternal pressure, thereby resulting in the underlying balloon 100 toprotrude through the aperture(s) 331. Alternatively or in additionthereto, the template 330 can have a “nominal diameter” that is lessthan the underlying balloon 100. The difference between the nominaldiameters being the approximate height of a protrusion 332. For example,the template 330 can be similarly formed from a wrapped film asdescribed herein; however, the film is wrapped to form a tubularprecursor at a diameter less than the diameter at which the tubularprecursor of balloon 100 can be formed. The apertures 331 can be formedin the template 330 in any suitable manner, e.g., laser cutting thetubular precursor.

Aperture 331 can comprise an opening or weakened site in the template330. In this regard, an opening can be a hole, cut, or any otherdiscontinuous section of the template 330. For example, a hole could beformed by puncturing template 330. Alternatively, aperture 331 cancomprise an area of template 330 where a portion of the templatematerial has been removed or otherwise weakened such that the weakenedportion at least partially deforms or detaches in response to inflationof balloon 100 and permits distension beyond the first inflated state.Apertures 331 can be formed by any suitable means, including cutting,stamping, laser cutting, perforating, and/or punching/puncturing and/orthe like. In various embodiments, the template 330 can comprise a netlike structure. The template 330 can comprise apertures 331 that vary insize or are the same size. In addition, decreasing the size theapertures can allow for a “coarser” balloon surface.

With reference to FIG. 4, a method of making a medical balloon inaccordance with the present disclosure can comprise wrapping a filmabout a mandrel at an angle at least about 75 degrees with respect to alongitudinal axis and up to about 88 degrees to form a tubular precursor(400). The wrapped film can be bonded and then removed as a tubularprecursor from said mandrel. Once formed, tension to the length of thetubular precursor can be applied to reduce its diameter (401). Invarious embodiments, at least a portion of the tubular precursor canthen be longitudinally compressed to reduce its length (402). Theprecursor can then be placed on an elongate member having a lumenwherein the precursor is in fluid communication with the lumen of theelongate member and secured thereto (403). The tubular precursor canoptionally be secured over a balloon catheter comprising a compliantbladder.

A pre-conditioning inflation can be performed by inflating the balloonto a nominal diameter (404). The inflation can be performed within aconcentric tubular form having an inner diameter approximately equal tothe nominal diameter of the balloon. The balloon and the balloon covercan be radially compacted to a delivery profile (405). The radialcompaction of the balloon cover forms random creases and folds in randomdirections.

With reference to FIG. 5 a method of using a medical balloon inaccordance with the present disclosure can comprise placing a balloon asdescribed herein in a vessel wherein the working length of the balloonextends along a curve of the vessel (500). The curvature of the vesselwould cause at least 20% total strain to the balloon wall and theballoon wall along an inner arc would have at least 5% compressivestrain upon inflation. Once in position, the balloon can be inflated(501) to at least 4 atm, at least 8 atm, at least 16 atm, at least 20atm, or more, or any range or value therebetween. In variousembodiments, inflating the balloon causes substantially uniform pressureto be applied to the surrounding vessel along the curve of the vessel(502). In various embodiments, inflating the balloon causessubstantially uniform contact to the surrounding vessel wall along thecurve of the vessel (503).

Example 1—Precursor Material

An expanded PTFE membrane—that is amorphously locked and generally madein accordance with U.S. Pat. No. 5,476,589 to Bacino which is herebyincorporated by reference in its entirety—had the following properties:Bubble point is approximately 138 kPa, thickness is approximately 6.3μm, mass per area is approximately 3 g/m², matrix tensile strength inthe strongest direction is approximately 907 mPa, matrix tensilestrength in the direction orthogonal to the strongest direction isapproximately 17.2 mPa. The precursor material was cut into a tape,wherein the strongest direction is along the length of the tape.

Example 2—Constructing Medical Balloon Comprising a Nominal Diameter of8 mm in Accordance with the Present Disclosure

A tubular precursor was formed as follows: The precursor material fromExample 1 having a 1.25 in slit width was helically wrapped about an 8.5mm mandrel at approximately 85 degrees relative to the longitudinal axisof the mandrel. The wraps were repeated on a bias in the oppositedirection to complete a total of four passes over a length of 100 mm.This tubular precursor was then thermally treated in an oven at 380° C.for 11 minutes and then removed from the oven. The tubular precursor wasremoved from the mandrel and axially stretched to decrease its diameterto about 1.8 mm. The tubular precursor was then placed on a mandrelhaving an outer diameter of about 1.8 mm and cut to 108 mm. The tubeassembly was then axially compressed to about 72% of its originallength.

A compliant polyurethane balloon catheter was obtained with a generallycylindrical balloon having a diameter of 5 mm and length of 60 mm(Bavaria Medizin Technologie GmbH (BMT), Oberpfaffenhofen, Germany). Thetubular precursor was slid over the balloon assembly (with the balloonin its collapsed state). The ends of the tubular precursor were securedto the catheter using LOCTITE® adhesive 4981 (Henkel Corporation,Düsseldorf, Germany) applied to an approximately 6 mm wide ePTFE tape asit was wrapped 15 times about the ends and the catheter body. Theballoon was then inflated to an approximate 8 mm diameter at 16atmospheres. With inflation medium in the balloon and the inflationvalve open, the tubular precursor, now a balloon cover, and compliantbladder were then radially compacted at 689 kPa to about the catheter.

Example 3—Compressive and Tensile Strain Test Method and Results

Test method: First, a 0.9 mm PTFE coated stainless steel mandrel wasinserted through the lumen of the balloon catheter to be tested. Theballoon was inflated to nominal inflation pressure. The inflation valvewas closed. The exterior surface of the working length of the balloonwas measured and marked around its circumference at 10 mm intervals. Theinflation valve was then opened and the balloon allowed to deflate. Themandrel was removed and replaced with a 0.035″ guidewire (AMPLATZ SUPERSTIFF® Guidewire, Boston Scientific, Natick, Mass., USA), ensuring thatthe flexible section of the guidewire was beneath the balloon portion ofthe catheter.

The balloon to be tested was then inserted into an 8 mm ID×12 mm ODpolyurethane tubing (Part number 50315K281, McMaster-Carr, Santa FeSprings, Calif., USA). The area in which the balloon was to bepositioned within the tube was lubricated with a light coat of releasecompound (Release Compound 7, Dow-Corning, Elizabethtown, Ky.). Thepolyurethane tubing was bent around a 60 mm diameter rod while holdingthe tubing tight against the outside circumference so that the balloonwas centered in the bent section of the tubing as shown in FIGS. 6a-6cand 7a-7c . The balloon was inflated within the tube to its rated burstpressure. A flexible ruler was bent around the rod adjacent the tube andthe spacing of the marks on the balloon on the inside arc of the bendwere measured, as shown in FIGS. 6c and 7c . The flexible ruler wassimilarly used to measure the marks across the outside arc of theballoon, as shown in FIGS. 6b and 7b . The measurements obtained areprovided in Table 1.

TABLE 1 Distance Distance between between marks on marks on CompressiveTensile Balloon the outside the inside Strain on Strain on BalloonPressures arc arc inside arc outside arc 8 mm × 62 mm 16 atm 12.25 mm 10mm  0% 22.5% standard (See FIG. 6b) (See FIG. 6c) BMT PTA balloon(Nylon, Lot 130327) 8 mm × 60 mm 16 atm  10.5 mm 8.5 mm  15%   5%balloon (See FIG. 7b) (See FIG. 7c) prepared in accordance with Example2)

Compressive strain was detected on the balloon made in accordance withExample 2, while none was detected on the BMT PTA balloon (BavariaMedizin Technologie GmbH (BMT), Oberpfaffenhofen, Germany).

Example 4—Method for Calculating Theoretical Compressive and TensileStrain

In order to obtain perspective on the strain values observed in Example3, the theoretical strain values required to maintain a neutral axis canbe compared to the observed values. The theoretical compressive andtensile strain values can be calculated based on the following. FIG. 10is a schematic of the test setup described in Example 3. Tubing 1000 isshown in a bent configuration. Neutral axis “NA” lies co-radially withtubing 1000. When a balloon having a catheter aligned co-radially isinserted into the tube 1000, the center axis of the balloon will matchthis neutral axis. The working length of the balloon will have an arclength aligned along the neutral axis. The angle θ is calculatedaccording to this formula:

θ=S/r, where S is the arc length, r is the radius, and theta is theangle in radians.

Using this approach, θ equals 1.56 radians if a balloon having a workinglength of 50 mm is inserted into the test apparatus and the bend has aradius of 32 mm (includes the wall thickness of tubing 1000).

To solve for the arc radius on the inside length of the balloon S_(i)(under compression) and the outside length of the balloon S_(o) (undertension) the following relationship is used:

S ₁ /r ₁ =θ=S ₂ /r ₂

For a balloon having a diameter of 8 mm and a 50 mm working length witha bend radius of 32 mm, assuming equal amounts of compressive andtensile strain, the inside arc length S_(i) is calculated by thefollowing: 32*50/(32+4)=S_(i)=44.44 mm. For the same balloon and radius,the outer arc length S_(o) is calculated by the following:(32+8)*50/(32+4)=S_(o)=55.56 mm. Therefore, S_(o) is 11.1% longer thanthe working length of the balloon along the neutral axis and S_(i) is11.1% shorter than the working length of the balloon along the neutralaxis.

Through a similar calculation, assuming all compressive strain, thetotal strain would be 20%, and when assuming all tensile strain, thetotal strain would be 25%. The 25% total strain on the outer arc isclose to that which was observed for the PTA Nylon balloon test inExample 3 at 22.5%.

Example 5—Method of Determining the Longitudinal and CircumferentialStiffness of a Balloon Wall and Test Results

Test Method: The balloon to be tested was inflated by placing a 100 mmsection of drawn ePTFE tubing over a pleated and folded balloon (8 mm×60mm) to form a cover. Movement of the cover was limited during inflationby ensuring cover material was clamped in a vice that wassupporting/clamping the catheter. The balloon was inflated and themid-balloon diameter was recorded with a laser micrometer. Once adiameter of 8 mm was achieved, the balloon was deflated. The cover isremoved from the balloon.

Next, for each longitudinal sample the cones of the balloon were cut sothat the sample was 50 mm long. The cuts were located in the flatworking length of the balloon and resulted in square edges. Each samplewas longitudinally slit with scissors to form a sheet and then trimmedto create a sample that was 50 mm long×20 mm wide. An INSTRON® tensiletester was set up with smooth grips, and the jaw pressure was set to 552kPa. The rate was set to 10 mm/min with a gauge length of 10 mm. Priorto loading the sample in the INSTRON® device, the width was taken in themiddle of the sample length. The gauge length of the specimen during thetesting was 10 mm. The test was set to run for 1 mm of crossheaddisplacement (˜10% strain). The resulting slope (i.e., force over changein length) was divided by the specimen width to obtain the stiffness, asthis response is not normalized per specimen thickness or % strain. Theslope was calculated in the region that matches the balloon tested“longitudinal” compliance. For example, if a balloon had a 3%longitudinal compliance (i.e., the percent of balloon lengthening wheninflated from the nominal inflation pressure to the rated burstpressure), the slope would be determined within the 3% strain region.

For each circumferential sample, after inflating the balloon asdescribed above, the cones of the balloon were cut within the flatworking length of the balloon but maximizing the sample length andresulting in square edges. The sample was further cut to form 2 annularsamples, each with a length of 10 mm. The INSTRON® device was set with acircumferential fixture. The rate was set to 10 mm/min and the gaugelength was set so that the fixtures were almost in contact with eachother. The test was set to run for 1 mm of crosshead displacement (˜8%strain). This resulting slope (i.e., force over change in length) wasdivided by the specimen width and multiplied by 2 to account for thehoop specimen to determine stiffness, as this response was notnormalized per specimen thickness or % strain. The slope was calculatedin the region that matches the balloon tested compliance. For example,if a balloon had a 3% circumferential compliance (i.e., the percent ofcircumferential diametric growth of the balloon when inflated from thenominal inflation pressure to the rated burst pressure), the slope wouldbe determined within the 3% strain region.

The above tests were performed on the following balloons: High PressurePTA Catheter, Creagh Medical Ltd, Galway, Ireland; “Fox” BalloonCatheter, p/n 12760-06, Abbott Vascular, Santa Clara, Calif., USA;“Workhorse” P/N 16500432; PTA Balloon Catheter, AngioDynamics, Latham,N.Y.; 3 conformable balloons prepared in accordance with Example 2 withprecursor materials as indicated below. The results are shown in FIG. 8.

Lo MD: An expanded ePTFE membrane—that is amorphously locked andgenerally made in accordance with U.S. Pat. No. 5,476,589 to Bacinowhich is hereby incorporated by reference in its entirety—had thefollowing properties: Bubble point is approximately 138 kPa, thicknessis approximately 6.3 μm, mass per area is approximately 3 g/m², matrixtensile strength in the strongest direction is approximately 917 mPa,matrix tensile strength in the direction orthogonal to the strongestdirection is approximately 17.2 mPa. The precursor material was cut intoa tape of 2.5 cm width, wherein the strongest direction is along thelength of the tape.

Med MD: An expanded ePTFE membrane—that is amorphously locked andgenerally made in accordance with U.S. Pat. No. 5,476,589 to Bacinowhich is hereby incorporated by reference in its entirety—had thefollowing properties: Bubble point is approximately 138 kPa, thicknessis approximately 6.3 μm, mass per area is approximately 3 g/m², matrixtensile strength in the strongest direction is approximately 834 mPa,matrix tensile strength in the direction orthogonal to the strongestdirection is approximately 36.5 mPa. The precursor material was cut intoa tape of 2.5 cm width, wherein the strongest direction is along thelength of the tape.

Hi MD: An expanded ePTFE membrane—that is amorphously locked andgenerally made in accordance with U.S. Pat. No. 5,476,589 to Bacinowhich is hereby incorporated by reference in its entirety—had thefollowing properties: Bubble point is approximately 138 kPa, thicknessis approximately 6.3 μm, mass per area is approximately 3 g/m², matrixtensile strength in the strongest direction is approximately 758 mPa,matrix tensile strength in the direction orthogonal to the strongestdirection is approximately 67.6 mPa. The precursor material was cut intoa tape of 2.5 cm width, wherein the strongest direction is along thelength of the tape.

Example 6—In Vivo Inflation of a Medical Balloon within a CurvedVasculature

The following balloons were each inflated in the bifurcated iliac of acanine model and the images were taken at the indicated pressures. Asshown in FIG. 9d , a Conquest balloon (P/N CQ-7586, Bard Medical, Tempe,Ariz.) was inflated to 10 atm and exhibited a kink in the working lengthand vessel straightening. The balloon could not be inflated to the ratedburst pressure because the observed degree of vessel straightening. Asshown in FIG. 9c , a semi-compliant balloon was inflated to 8 atm andexhibits vessel straightening. The balloon could not be inflated to therated burst pressure because the observed degree of vesselstraightening. As shown in FIGS. 9a and 9b , the conformable balloonprepared in accordance with Example 2 exhibited kink-free inflation andimproved conformance to the curved vessel at both 10 atm and at 18 atm.

Example 7—Constructing Medical Balloon Comprising a Nominal Diameter of3 mm in Accordance with the Present Disclosure

A tubular precursor was formed as follows: The precursor material fromExample 1 at a 0.5 inch slit width was helically wrapped about an 3.25mm mandrel at 76 degrees relative to the longitudinal axis of themandrel. The wraps were repeated on a bias in the opposite direction tocomplete a total of six passes. This tubular precursor was thenthermally treated in an oven at 380° C. for 5 minutes and then removedfrom the oven. The tubular precursor was removed from the mandrel andaxially stretched to decrease its diameter to about 1.8 mm. The tubularprecursor was then placed on a mandrel having an outer diameter of about1.8 mm and cut to 87 mm. The balloon working length portion of the tubeassembly was then axially compressed to about 90% of its originallength.

A compliant polyurethane balloon catheter was obtained with a generallycylindrical balloon having a diameter approximately 5 mm and length of60 mm (Bavaria Medizin Technologie GmbH (BMT), Oberpfaffenhofen,Germany). The tubular precursor was slid over the balloon assembly (withthe balloon in its collapsed state). The ends of the tubular precursorwere secured to the catheter using LOCTITE® adhesive 4981 (HenkelCorporation, Düsseldorf, Germany) applied to an approximately 6 mm wideePTFE tape as it was wrapped 15 times about the ends and the catheterbody. The balloon was then inflated to an approximate 3 mm diameter atapproximately 10 atmospheres. With inflation medium in the balloon andthe inflation valve open, the tubular precursor, now a balloon cover,and compliant bladder were then radially compacted at approximately 689kPa to about the catheter.

Example 8—Constructing Medical Balloon Comprising a Nominal Diameter of5 mm in Accordance with the Present Disclosure

A tubular precursor was formed as follows: The precursor material fromExample 1 having a 1 inch slit width was helically wrapped about an 5.2mm mandrel at 81 degrees relative to the longitudinal axis of themandrel. The wraps were repeated on a bias in the opposite direction tocomplete a total of four passes. This tubular precursor was thenthermally treated in an oven at 380° C. for 7 minutes and then removedfrom the oven. The tubular precursor was removed from the mandrel andaxially stretched to decrease its diameter to about 1.8 mm. The tubularprecursor was then placed on a mandrel having an outer diameter of about1.8 mm and cut to 108 mm. The balloon working length portion of the tubeassembly was then axially compressed to about 80% of its originallength.

A compliant polyurethane balloon catheter was obtained with a generallycylindrical balloon having a diameter of 5 mm and length of 60 mm(Bavaria Medizin Technologie GmbH (BMT), Oberpfaffenhofen, Germany). Thetubular precursor was slid over the balloon assembly (with the balloonin its collapsed state). The ends of the tubular precursor were securedto the catheter using LOCTITE® adhesive 4981 (Henkel Corporation,Düsseldorf, Germany) applied to an approximately 6 mm wide ePTFE tape asit was wrapped 15 times about the ends and the catheter body. Theballoon was then inflated to an approximate 5 mm diameter atapproximately 12 atmospheres. With inflation medium in the balloon andthe inflation valve open, the tubular precursor, now a balloon cover,and compliant bladder were then radially compacted at approximately 689kPa to about the catheter.

Example 9—Constructing Medical Balloon Comprising a Nominal Diameter of8 mm in Accordance with the Present Disclosure

A tubular precursor was formed as follows: The precursor material fromExample 1 having a 1.25 inch slit width was helically wrapped about an8.5 mm mandrel at approximately 85 degrees relative to the longitudinalaxis of the mandrel. The wraps were repeated on a bias in the oppositedirection to complete a total of four passes. This tubular precursor wasthen thermally treated in an oven at 380° C. for 11 minutes and thenremoved from the oven. The tubular precursor was removed from themandrel and axially stretched to decrease its diameter to about 1.8 mm.The tubular precursor was then placed on a mandrel having an outerdiameter of about 1.8 mm and cut to 135 mm. The balloon working lengthportion of the tube assembly was then axially compressed to about 70% ofits original length.

A compliant polyurethane balloon catheter was obtained with a generallycylindrical balloon having a diameter of 5 mm and length of 60 mm(Bavaria Medizin Technologie GmbH (BMT), Oberpfaffenhofen, Germany). Thetubular precursor was slid over the balloon assembly (with the balloonin its collapsed state). The ends of the tubular precursor were securedto the catheter using LOCTITE® adhesive 4981 (Henkel Corporation,Düsseldorf, Germany) applied to an approximately 6 mm wide ePTFE tape asit was wrapped 15 times about the ends and the catheter body. Theballoon was then inflated to an approximate 8 mm diameter at 16atmospheres. With inflation medium in the balloon and the inflationvalve open, the tubular precursor, now a balloon cover, and compliantbladder were then radially compacted at 689 kPa to about the catheter.

Example 10—Constructing Medical Balloon Comprising a Nominal Diameter ofApproximately 12 mm in Accordance with the Present Disclosure

A tubular precursor was formed as follows: The precursor material fromExample 1 having a 1.25 inch slit width was helically wrapped about a 13mm mandrel at 86 degrees relative to the longitudinal axis of themandrel. The wraps were repeated on a bias in the opposite direction tocomplete a total of six passes. This tubular precursor was thenthermally treated in an oven at 380° C. for 17 minutes and then removedfrom the oven. The tubular precursor was removed from the mandrel andaxially stretched to decrease its diameter to about 1.8 mm. The tubularprecursor was then placed on a mandrel having an outer diameter of about1.8 mm and cut to 185 mm. The balloon working length portion of the tubeassembly was then axially compressed to about 55% of its originallength.

A compliant polyurethane balloon catheter was obtained with a generallycylindrical balloon having a diameter of 5 mm and length of 60 mm(Bavaria Medizin Technologie GmbH (BMT), Oberpfaffenhofen, Germany). Thetubular precursor was slid over the balloon assembly (with the balloonin its collapsed state). The ends of the tubular precursor were securedto the catheter using LOCTITE® adhesive 4981 (Henkel Corporation,Düsseldorf, Germany) applied to an approximately 6 mm wide ePTFE tape asit was wrapped 15 times about the ends and the catheter body. Theballoon was then inflated to an approximate 12 mm diameter atapproximately 5 atmospheres. With inflation medium in the balloon andthe inflation valve open, the tubular precursor, now a balloon cover,and compliant bladder were then radially compacted at 689 kPa to aboutthe catheter.

Example 11—Comparison Study of Straightening Force of Medical Balloonsas Measured in 3-Point Bend Fixture

Test Method: In order to measure the straightening force, an Instron®3-point bend fixture with an Instron® 100N load cell was set up, suchthat the balloon to be tested would have a bend radius that wouldachieve a 16% theoretical strain (according the equation described inExample 4) at the nominal inflation pressure. The setup of the Instron®3-point bend fixture is shown in FIGS. 11a to 11d for the 3 mm, 5 mm, 8mm, and 12 mm balloon, respectively. The dimensions shown in FIGS. 11ato 11d are in millimeters.

Prior to testing, each balloon was conditioned by submersing in a 37° C.water bath for 2 minutes. Once conditioned, a guidewire (Amplatz, 0.035″Super Stiff) was inserted into to catheter of the balloon such that the“floppy” end was aligned with the balloon portion. A pressure gauge andindeflator was connected to the catheter. The sample was inserted intothe 3-point bend fixture in a curved conformation approximate theappropriate bend radius. Each balloon was inflated to pressures spanningthe working pressure range and as shown in the table of data provided inFIG. 12. Each balloon was held at each pressure for 10 seconds exceptfor the rated burst pressure, which was held for 30 seconds. The forcewas measured continuously throughout the entire test with mean force foreach pressure provided in FIG. 12. The working pressure range for the 3mm balloon of Example 7 was 10 atm to 17 atm. The working pressure rangefor the 5 mm balloon of Example 8 was 9 atm to 17 atm. The workingpressure range for the 8 mm balloon of Example 9 was 6 atm to 16 atm.The working pressure range for the 12 mm balloon of Example 10 was 5 atmto 8 atm.

The above test was performed on the following balloons: “Conquest”Balloon Catheter, P/N CQ-7586, Bard Medical, Tempe, Ariz.; “FoxCross”Balloon Catheter, P/N 10324-80 (3 mm), 10326-60 (5 mm), 10329-60 (8 mm),10332-60 (12 mm), Abbott Vascular, Santa Clara, Calif., USA; “Workhorse”P/N 16500432; PTA Balloon Catheter, AngioDynamics, Latham, N.Y.; and 4balloons prepared in accordance with Examples 7-10.

Plots of the balloons tested are provided in FIGS. 13a-13d . As shown ineach of these figures, the observed rate of change of the straighteningforce per unit of pressure is much lower for each of the conformableballoons (prepared in accordance with Examples 7-10) as compared to theAbbott FoxCross having the same diameter. As shown in FIG. 13c , inparticular, the conformable balloon prepared in accordance with Example9 demonstrated the lowest rate of change of the straightening force perunit of pressure as compared to other PTA balloons sold by Bard, Abbott,and Angiodynamics.

This example demonstrates that medical balloons—made in accordance withthe present disclosure and having a nominal diameter between about 3 mmto about 8 mm and a nominal inflation pressure at or below 10atm—exhibit less than a 13% increase in mean straightening force wheninflated from a pressure of 10 atm to 14 atm while in a curvedconformation requiring 16% total strain. In addition, such balloonsexhibit a mean straightening force of less than 5 N when inflated up toa pressure of 17 atm while in a curved conformation requiring 16% totalstrain. Specifically, under such conditions, the 5 mm diameter balloonexhibited a mean straightening force of less than 4N, and the 8 mmdiameter balloon exhibited less than 5N.

Similarly, medical balloons—made in accordance with the presentdisclosure and having a nominal diameter between about 9 mm to about 12mm and a nominal pressure at or below 6 atm—exhibit less than a 3Nincrease in mean straightening force when inflated from a pressure of 5atm to 8 atm while in a curved conformation requiring 16% total strain.In addition, such balloons exhibit a mean straightening force of lessthan 8 N when inflated up to a pressure of 8 atm while in a curvedconformation requiring 16% total strain.

Moreover, it can be inferred from this example, that a medicalballoon—made in accordance with the present disclosure and having anominal diameter between about 13 mm to about 14 mm and a nominalinflation pressure at or below 6 atm—exhibits less than about 3.5Nincrease in mean straightening force when inflated from a pressure of 6atm to 8 atm while in a curved conformation requiring approximately 16%total strain. In addition, such balloons can exhibit a meanstraightening force of less than 11 N when inflated up to 8 atm while ina curved conformation requiring 16% total strain.

FIG. 14a is a graph plotting the straightening force at the rated burstpressure for the 3, 5, 8, and 12 mm conformable balloon. Based on thisdata, predictive trend lines of a maximum straightening force at therated burst pressure for balloons ranging from 3-12 mm are plotted. Aconformable balloon of the present disclosure within about 3 to about 12mm in diameter will have a straightening force at the rated burstpressure that can be less than 0.86 (Diameter)+0.20; less than 0.74(Diameter)+0.49; or even less than 0.66 (Diameter)+0.64. The trend lineformulas are based on the following increases (see Table 2) to theobserved 3 mm straightening force at rated (2.575 N) and the observed 12mm straightening force at rated (7.8 N).

TABLE 2 Trend line formula % increase at 3 mm % increase at 12 mm0.86(Diameter) + 0.20 8 35 0.74(Diameter) + 0.49 5 20 0.66(Diameter) +0.64 2 10

Numerous characteristics and advantages have been set forth in thepreceding description, including various alternatives together withdetails of the structure and function of the devices and/or methods. Thedisclosure is intended as illustrative only and as such is not intendedto be exhaustive. For example, embodiments of the present disclosure aredescribed in the context of medical applications but can also be usefulin non-medical applications. It will be evident to those skilled in theart that various modifications may be made, especially in matters ofstructure, materials, elements, components, shape, size, and arrangementof parts including combinations within the principles of the invention,to the full extent indicated by the broad, general meaning of the termsin which the appended claims are expressed. To the extent that thesevarious modifications do not depart from the spirit and scope of theappended claims, they are intended to be encompassed therein.

What is claimed is:
 1. A medical balloon comprising: a balloon wallcomprising a porous material; a nominal diameter of between about 9 mmto about 12 mm and a working pressure range that spans a nominalinflation pressure to a rated burst pressure, wherein the medicalballoon exhibits less than a 3N increase in mean straightening forcewhen inflated across the working pressure range while in a curvedconfiguration requiring 16% total strain.
 2. The medical balloon ofclaim 1, wherein the balloon exhibits a mean straightening force lessthan 10N at the rated burst pressure while in the curved configurationrequiring 16% total strain.
 3. The medical balloon of claim 1, whereinthe medical balloon remains kink-free when inflated in the curvedconfiguration.
 4. The medical balloon of claim 1, wherein polymericmaterial comprises expanded polytretrafluoroethylene (ePTFE).
 5. Themedical balloon of claim 1, wherein the balloon exhibits a meanstraightening force less than 10N at a pressure of 8 atm while in thecurved configuration requiring 16% total strain.
 6. The medical balloonof claim 1, wherein the nominal inflation pressure is greater than 4atm.
 7. The medical balloon of claim 1, wherein the mean straighteningforce is determined with a 3-point bend fixture.
 8. A medical ballooncomprising: a balloon wall comprising a porous material; a nominaldiameter of between about 9 mm to about 12 mm and a working pressurerange that spans a nominal inflation pressure to a rated burst pressure,wherein the medical balloon exhibits less than a 10N mean straighteningforce when inflated across the working pressure range while in a curvedconfiguration requiring 16% total strain.
 9. The medical balloon ofclaim 8, wherein the working pressure range for the medical balloon isbetween about 5 atm and about 8 atm.
 10. The medical balloon of claim 8,wherein the medical balloon exhibits a mean straightening force lessthan 10N at the rated burst pressure while in a curved configurationrequiring 16% total strain.
 11. The medical balloon of claim 8, whereinthe mean straightening force is determined with a 3-point bend fixture.12. The medical balloon of claim 8, wherein the medical balloon remainskink-free when inflated in the curved configuration requiring 16% totalstrain.
 13. The medical balloon of claim 8, wherein the medical balloonexhibits less than an 8N mean straightening force when inflated up to apressure of 8 atm while in a curved configuration requiring 16% totalstrain.
 14. The medical balloon of claim 8, wherein the nominalinflation pressure is less than 6 atm.
 15. A medical balloon comprising:a balloon wall comprising a porous material, a nominal diameter ofbetween about 13 mm to about 14 mm and a working pressure range thatspans a nominal inflation pressure to a rated burst pressure, whereinthe medical balloon exhibits less than a 12N mean straightening forcewhen inflated across the working pressure range while in a curvedconfiguration requiring 16% total strain.
 16. The medical balloon ofclaim 15, wherein the balloon exhibits less than an 11N meanstraightening force when inflated up to a pressure of 8 atm while in acurved configuration requiring 16% total strain.
 17. The medical balloonof claim 15, wherein the medical balloon remains kink-free when inflatedin the curved configuration.
 18. The medical balloon of claim 15,wherein porous material comprises ePTFE.
 19. The medical balloon ofclaim 15, wherein the nominal inflation pressure is less than 6 atm. 20.The medical balloon of claim 15, wherein the mean straightening force isdetermined with a 3-point bend fixture.